The invention relates to hatch vent assemblies and more particularly to a hatch cover vent assembly for use on covered hopper railway cars, and the like, used to carry various types of lading. Such railway cars typically have a number of hoppers into which lading is loaded through an opening or hatchway in the roof of the car. The hatchway is provided with a hatch cover, typically circular, which is adapted to be sealed in an airtight manner with a circular coaming at the top of the hatchway. In order to seal and latch the hatch cover in place there is typically provided a locking strap or arm which extends across the hatch cover to exert a downward force thereon and which can be locked to prevent tampering with the lading. In some cases, it is desirable to provide an air vent to the interior of the hopper car in order to prevent the build up of pressure differentials within the sealed hopper. These pressure differentials may develop due to temperature changes within the hopper during transport and other causes.
It is important that the vent be constructed in such a way as to prevent environmental containments from entering into the hopper and possibly ruining the lading. The most commonly encountered environmental contaminants are rain and snow; however, wind borne solids such as plant seeds and insects must also be prevented from entering the hopper through the air vent.
It is well known to provide an air vent passage through a hatch cover of a hopper car. An example of such a prior art vent structure for a hopper car is shown in U.S. Pat. No. 4,819,830, the disclosure of which is incorporated herein by reference. Other vent structures are shown in U.S. Pat. Nos. 4,127,216 and 4,609,126.
The vent structures of the prior art have been somewhat complicated, bulky and relatively expensive to manufacture, since a great deal of metal materials are used to construct the vent.